Well tools

ABSTRACT

A well safety valve system controllable from the surface and adapted for installation in a well to replace a malfunctioning existing system or for conversion of a well not having a safety system. The safety valve system includes a first outer tubing string extending from a well head to the desired production zone in the well and a second inner tubing string concentrically disposed within the outer tubing string and releasably locked at the lower end thereof with the outer tubing string whereby the inner tubing string is inserted and withdrawn by manipulation from the surface. A safety valve is supported at the lower end of the inner tubing string for shutting off fluid flow into the tubing string responsive to predetermined flow conditions. The safety valve is held in an open position by fluid pressure transmitted from the surface to the valve through the annulus between the outer and inner tubing strings. In one form of the invention the outer tubing string has a landing nipple incorporated in the string at the safety valve depth and the inner tubing string includes a locking collet engageable with the landing nipple recess for locking the lower end of the inner tubing string at the landing nipple within the outer string. The inner string also has a landing nipple for the releasable locking of a safety valve which holds the inner tubing string locking collet engaged with the outer tubing string. Another form of the invention includes a landing nipple assembly releasably lockable in the smooth bore of the outer tubing string with the removable landing nipple being engaged by the inner tubing string which also has landing nipple means for supporting the safety valve. The safety valve holds the locking collet of the inner tubing string locked with the releasable landing nipple. In a still further form of the invention a removable landing nipple for releasably locking the inner tubing string within the outer tubing string is releasably locked in a landing nipple provided in the outer tubing string at the desired depth. In each installation and the well procedure therefor a plug is used for shutting the well in at the safety valve depth while running and retrieving the inner tubing string.

United States Patent 1191 Taylor WELL TOOLS [75] Inventor: Frank H.Taylor, Carrollton, Tex.

[73] Assignee: Otis Engineering Corporation,

, Dallas, Tex.

[22] Filed: May 10, 1971 [21] Appl. No.: 141,922

Primary Examiner-James A. Leppink Attorney-H. Mathews Garland [57]ABSTRACT A well'safety valve system controllable from the surface andadapted for installation in a well to replace a malfunctioning existingsystem or for conversion of a well not having a safety system. Thesafety valve system includes a first outer tubing string extending froma well head to the desired production zone in the well and a secondinner tubing string concentrically dis- [111 3,747,682 1461 July 24,1973 4 posed within the outer tubing string and releasably string forshutting off fluid flow into the tubing string responsive topredetermined flow conditions. The

safety valve is held in an open position by fluid pressure transmittedfrom the surfaceto the valve through the annulus between the outer andinner tubing strings. In

one form of the invention the outer tubing string has a landing nippleincorporated in the string at the safety valve depth and the innertubing string includes a locking collet engageable with the landingnipple recess for locking the lower end of the inner tubing string atthe landing nipple within the outer string. The inner string also has alanding nipple for the releasable locking of a safety valve which holdsthe inner tubing string locking collet engaged with the outer tubingstring. Another form of the invention includes a landing nipple assemblyreleasably lockable in the smooth bore of the outer tubing string withthe removable landing nipple being engaged by the inner tubing stringwhich also has landing nipple means for supporting the safety valve. Thesafety valve holds the locking collet of the inner tubing string lockedwith the releasable landing nipple. In a still further form of theinvention a removable landing nipple for releasably locking the innertubing string within the outer tubing stringis releasably locked in alanding nipple provided in the outer tubing string at the desired depth.In each installation and the well procedure therefor a plug is used forshutting the well in at the safety valve depth while running andretrieving the inner tubing string.

25 Claims, 28 Drawing Figures United States Patent 1 [11.1 3,747,682

Taylor July 2 4, 1973 WELL TOOLS This invention relates to well toolsand more particularly relates to safety valve systems for wells.

In the past, well systems, particularly those adapted to the productionof oil, have often been equipped with well safety valve systems whichwere installed at the time of the initial completion and fitting of thewell. Such well systems can be very expensive in terms of both shut-downtime and servicing requirements upon either failure or malfunction ofthe safety valve systems. The reworking of the well can be a major taskwhen it is necessary to pull the tubing strings toreplace the safetyvalve equipment. In one form of such safety valve system the fluidpressure required to maintain the valve in an open position is conductedto the valve through a small tubing extending alongside the main tubingstring in which the safety valve is supported and through which the wellis produced. A rupture of this control fluid line necessitates pullingthe tubing string. In other situations wells may be completed withoutthe installation of a safety valve and changing conditions subsequentlyrequire the use of a safety valve. Presently available systems, both forthe repair of an existing safety valve arrangement or for the conversionof a well to safety equipment, requiresa major workover of the well dueto the absence of readily convertible or repairable components.

It is, therefore, a particulary important object of the invention toprovide a new and improved well safety valve system. It is anothe objectof the invention to provide a well safety valve system which is used forthe conversion of both malfunctioning existing systems and also wellsnot initialy equipped with any form of safety valve system. It is afurther object of the invention to provide a well safety valve systemcontrollable from the surface by control fluid pressure communicated toa safety valve in the well through an annular space around theproduction tubing of the well. It is a still further object of theinvention to provide a well safety valve system of the characterdescribed wherein the safety valve is releasably supported at the lowerend of an inner production tubing string in an outer tubing string. Itis still another object of the invention to provide a well safety valveof the character described wherein the safety valve is inserted andremoved through a removable inner tubing string without removal of theinner tubing string. It is a still further object of the invention toprovide a safety valve system of the character described which includesa removable inner tubing string for supporting the well safety valveusable in an outer tubing string equipped with landing nipple means. Itis a still further object of the invention to provide a well safetyvalve system of the character described which includes a removablelanding nipple releasably lockable in an outer tubing string andengageable by a releasable inner tubing string for supporting the safetyvalve at the desired depth. It is a still further objectof the inventionto provide a well safety valve system of the character described whichincludes a landing nipple releasably lockable along a smooth wall boreof an outer tubing stringand engageable by a releasable inner tubingstring for supporting the safety valve at the desired depth. It is astill further object of the invention to provide a method of fitting anexisting well with a safety valve system.

In accordance with the invention there is provided a well safety valvesystem including an outer tubing string supported in a well casing, aninner tubing string releasably supported within the outer tubing stringand defining an annular flow passage between such tubing strings, and awell safety valve releasably supported at the lower end of the innertubing string and communieating with the annular space between thetubing strings for operating the safety valve responsive to fluidpressure in the annular space. The inner production tubing stringsupporting the safety valve is inserted and removed without handling theouter tubing string. The safety valve holds the inner tubing stringlocked in the outer tubing string. In one form of the invention theouter tubing string is initially equipped with a landing nippleengageable by locking means at the lower end of the inner tubing string.In another form of the invention a releasable landing nipple is securedwith an outer tubing string landing nipple and engaged by locking meanson the lower end of the inner tubing string which supports a removablesafety valve at the lower end thereof. In a still further form of theinvention a releasable landing nipple for holding the lower end of theremovable inner tubing string is adapted to engage the smooth wall boreof the outer tubing string for installations where the outer tubingstring was not initially equipped with a landing nipple.

The invention, together with its objects and advantages, will be morereadily understood from reading the following descriptiontaken inconjunction with the accompanying drawings wherein:

FIG. 1 is a broken longitudinal schematic drawing in section of a wellincluding a system having safety valve apparatus embodying theinvention;

FIGS. Z-A and 2-H, taken together, constitute a longitudinal view insection and elevation of an existing well safety valve systemconvertedto a safety system embodying the invention;

FIG. 3 is a fragmentary view in elevation of the section of the innertubing string of the system of FIG. 2-A

showing the locking collet fingers: formed in the inner tubing string;

FIGS. 4-A and 4-H together constitute a longitudinal view in section andelevation of another form of well safety valve system embodying theinvention;

FIGS. 5-A, S-B, and S-C together comprise a longitudinal view in sectionand elevation of a still further form of well safety valve systemembodying the invention and illustrating the lower stop in place and theremovable landing nipple being set;

FIGS. 6-A, 6-B, and 6-C together are a view in section and elevation ofthe well system of FIGS. 5-A, 5-H, and S-C with the landing nipple set;

FIGS. 7-A, 7-B, and 7-C together constitute a longitudinal view insection and elevation of the well system of FIGS. 5-A through 6-C withthe well plug set in-the landing nipple;

FIGS. 8-A, 8-H, and 8-C, taken together, constitute a longitudinal viewin section and leleaation of the well system of FIGS. S-A through 7-C,'illustrating the well plug removed and the safety valve installed;v

FIGS. 9-A, 9-B, and 9'-C, taken together, constitute a view in sectionand elevation of another form of well landing valve system emboding theinvention with only the removablelanding nipple of the system set in theouter well tubing;

FIGS. l-A, -8, and 10-(1, taken together. comprise a longitudinal viewin section and elevation of the well system of FIGS. 9-A through 9-Cwith the removable inner tubing and a well plug releasably engaged withthe removable landinl nipple of the system;

FIGS. ll-A, ll-B, and ll-C comprise a longitudinal view in section andelevation showing the well system of FIGS. 9-A through 10-C with theplug removed and the safety valve installed; and

FIG. 12 is an exploded view in elevation of the locking collet assemblyon the removable landing nipple of the well system of FIGS. 9-A through11-C.

Referring to the drawings FIG. 1 illustrates schematically the form ofthe invention shown in FIGS. 2-A and 2-B. The well system shown in FIG.1 includes a well casing 21 of suitable conventional design installed bystandard methods in a well 22 and provided with a top closure flange 23.A tubing hanger 24 is supported on the flange 23 and provided with afluid conduit 25 for communicationinto the casing of the well as desiredduring various procedures performed on the well. An outer tubing stringis supported in hanging relationship from the hanger 24 extendingdownwardly in the well casing to a desired depth therein. At the depthat which a well safety valve may be desired the outer tubing string 30is provided with a landing nipple 31 having locking recesses 32. Aninner tubing string 33 is supported within the outer tubing string froma hanger 34 mounte on the hanger 24. The inner tubing string has lockingcollet fingers 35 formed along a lower end portion releasably lockingthe lower end of the tubing string wih the locking recess 32 of thelanding nipple 31 in the outer tubing string. The inner tubing string isinsertable and withdrawable relative to the outer tubing string withoutdisturbing the outer tubing string. The inner tubing string is providedwith a locking recess near the lower end thereof fr releasably locking astandard fluid-operated well safety valve 41 in the tubing string tocontrol flow from below the safety valve into the inner tubing stringthrough which well fluids are produced. The inner tubing stirng has aside port 42 communicating with the annulus 43 defined between the innerand outer tubing strings and extending to the surface into the hanger34. A control fluid line 44 is connected through the hanger 34 into theannulus 43 for communicating control fluid under pressure from thesurface through the annulus to the well safety valve 41. Most standdequipment and procedures require that this control fluid be used to holdthe safety valve at an open position. The line 44 is connected to safetyequipment, not shown, including an Otis Surface Control Manifold asillustrated and described at page 3,887 of the 1970-197] issue of theComposite Catalog of Oil Field Equipment and Services" published byWorld Oil, Houston, Tex. Such a control manifold may be operativeresponsive to a number of monitored operating conditions for shuttingdown the well in the event of a break in the line, a fire, and manyother situations involving the need for closing in the well. A mastervalve 44 is supported on the inner casing hanger 34 for controlling flowof well fluids from the well. The safety valve 41 and the removableinner tubing string 33 are installed and retrieved utilizing equimentand procedures' discussed in more detail in connection with the specificembodiments of the well safety valve systems illustrated in thedrawings. While the system broadly illustrated schematically in FIG. 1is exemplary of the system shown more specifically in FIGS. 2-A and 2-B,the broad concept represented in FIG. 1 ofa well safety valve system isequally applcable to the other systems shown in the other figures of thedrawings wherein removable landing nipples are employed for releasableengagement with the outer well tuing.

FIGS. 2-A, 2-B, and 3 illustrate a form of well safety valve systemuseful to convert an existing safety valve system to a system embodylngthe invention. The outer tubing string 30 is supported from the tubinghead 24. The tubing string 30 includes the landing nipple 31 having theinternal annular locking recess 32. The landing nipple has a side portfitting 53 which is connected with a control fluid line 54 extending inthe original well installation to the surface to control fluid pressureequipment, not shown, for providing fluid pressure control of a safetyvalve, not shown, supported directly in the landing nipple 31. Thepresent well system represents a conversion to one embodying theinvention subsequent to some failure or malfunction of the originalsafety system wherein the control line 54 functioned. The control fluidin the original system was communicated to the safety valve used in thatsystem through the landing nipple side port 55. Referring to FIG. 2-B,the tubing string 30 includes lower sections, not shown, connected by acoupling 60 into the tubing string with the lower sections being of areduced diameter. A section 62 of the tubing string 30 threaded on thelower end of the landing nipple 31 includes an internal annular landingshoulder 63 which is engaged by the lower end of the internal tubingstring 33. The inner tubing string includes a lower locking and landingnipple section 65 which comprises the lower end portion of the innertubing string provided with internal locking recesses and the laterallymovable locking collet fingers 35 which are machined along the side wallof the tubing section integral with the tubing as evident in FIG. 3. Theinner tubing section 65 is also provided with two sets of spacedexternal O-ring seals 72 and 73 positioned to seal above and below theside port 55 of the outer tubing string landing nipple 31 so that whenthe inner tubing section is in place the port 55 is effectively isolatedfrom the bore of the outer tubing string, thus blocking off theinoperative original source of safety valve control fluid. The lockingcollet fingers 35 of the inner tubing string section are disposedlongitudinally to move laterally to engage the internal locking recess32 of the outer tubing string landing nipple when the lower end of theinner tubing string rests on the landing shoulder 63 of the outer tubingstring.

The inner tubing string 33 is concentrically spaced within the outertubing string 30 to define the control fluid annulus 43 which extendsfrom the surface at the well head to communicate control fluid from theline 44 downwardly into the safety valve 41 supported,

within the landing nipple portion of the inner tubing string. Thestructure of the landing nipple portion of the inner tubing stringwhereby the locking collet fingers 35 are formed along the wall of thetubing string section provides eircumferentially spaced inverted U-shaped openings 75 which permit the control fluid to communicate throughthe inner tubing string from the annulus for control of the safety valve41 supported in the string. The wireline insertable and removable safetyvalve 41 has laterally expandable and contractible locking dogs or keys41 releasably locked in the inner tubing string and controls well fluidsthrough the bore of the inner tubing string. The locking keys of thesafety valve are received within the locking recesses70 of the landingnipple portion 65 of the inner tubing string. The safety valve isprovided with upper and lower external seal assemblies 82 and 83,respectively, for sealing around the valve within the inner tubingstring landing nipple portion above and below the slots 75 at the colletfingers 35 so that valve control fluid communicated through the annulus43 and the slots 75 is confined within the inner tubing string betweenthe seals 82 and 83 for communication through the side port 84 in thesafety valve for remote fluid control of the valve. The safety valvebody along a central portion 85 is disposed in alignment with the headsof the collet fingers 35 preventing inward contraction of the colletfingers and thereby locking the fingers at the recess 32 so that theinner tubing string is locked within the outer tubing string when thesafety valve is in place within the inner tubing string A wellinstallation of the nature of that shown in FIGS. 2-A and 2 B,generally, initially includes a safety valve, not shown, installedwithin the landing nipple 31 of the outer tubing string and controlledby fluid conducted through the line 44 and the side port 55 to thesafety valve. When failure of this well system, such as rupture of theline 54, occurs, the well system is readily converted to a safety valvearrangement embodying the present invention. The original safety valveis removed by suitable means and a standard tubing plug, not shown, isinstalled in the outer tubing section below the coupling 60 of FIG. 2-Bby standard wireline procedures. As previously explained, this lowerportion of the outer tubing string is of a smaller diameter and thusaccommodates a plug which ultimately can be removed by wirelinethroughthe bore of the inner tubing string. With the well plug set in the outertubing string below the coupling 60, the well is, of course, shut inabove the plug and the pressure is bled off at the well head to permitthe well to be opened for the insertion of the inner tubing string 64,which, preferably, is not run in through a-stuffing box because it issubstantial in diameter and may be quite long for such an insertionprocedure. With the well thus shut-in, the well head is opened and theinner tubing string 64 is lowered into the well'until its lower endengages the landing shoulder 63 in theouter tubing section 62. Thecollet fingers 35 are aligned with and spring outwardly into lockingrelationship in the recess 32 of the outer tubing string landing nipple51. the seals 72 and 73 of the inner tubing string seal above and belowthe port 55 to prevent communication through the ruptured control line54 into the bore of the outer tubing string. The pressure is thenequalized across the well plug so that the well is again under pressureto the surface. Wireline procedures are then used to remove the plugthrough the inner tubing string. The safety valve 41 is then run bywireline into the inner tubing string until it is properly positioned atand the locking keys 40 of thevalve expand into the locking recesses 70of he landing nipple 31 of the inner tubing string. Control fluid isthen introduced into the annulus 43 through the line44 at the well head.The fluid flows downwardly in the annulus and radially inwardly throughthe slots 75 around the collet fingers. The fluid under pressure iscommunicated around the safety valve'between its seals 82 and 83 intothe valve through the side port 84. When the pressure is raised to asufficient level, the safety valve opens to permit production throughthe inner tubing string. When the pressure of the control fluid dropsbelow a predetermined level because of such factors as a tire, ablowout, or other malfunction at the surface, the reduced pressurepermits the safety valve to close. In removal of the safety valve systemof the present invention, the valve 41 is first retrieved by wirelinefrom the inner tubing string. A well plug is again run into the well andlocked in the outer tubing string below the lower end of the'innertubing string. With the well shut in, the well head is opened and theinner tubing string is withdrawn. Upward force on the inner tubingstring cams the collet fingers 35 inwardly, releasing the inner tubingstring from the recess 32 permitting it to be lifted to the surface.During the presence of the safety valve within the inner tubing stringlanding nipple the valve body portion 85 holds the inner tubing stringcollet fingers expanded in the outer tubing string locking recess 32 sothat the inner tubing string cannot be released and lifted to thesurface. The safety valve is thus locked within the lower end portion ofthe inner tubing string while the inner tubing string is locked withinthe outer tubing string so that when the safety valve closes effecting alarge pressure differential across the valve tending to lift the valveand the inner tubing string within the outer tubing string, the valveand inner tubing string are locked in position by virtue of the colletfingers 35 and the valve locking keys 40. FIGS. 4-A and 4-B illustrateanother form of well safety valve system embodying the invention whichpermits the conversion of a well system not originally equipped with asafety valve. The original well installation includes an outer tubingstring including a coupling 91 into which is threaded a landing nipple92 having an internal locking recess 93 and secured at its lower end ona reduced landing nipple 94 having an internal locking recess 95.Additional portions of the outer tubing string include a couplingthreaded on the landing nipple 94 and a tubing section 101 connectedwith the coupling. a

In accordance with the present invention, an inner tubing string 102 isreleasably locked within the outer tubing string held by a standardsafety valve 103 which is releasably locked within the inner tubingstring. The safety valve is adapted for fluid control and wirelinehandling. The inner tubing string includes a coupling 104 threaded onanother section 105 which is threaded into a tubular locking fittinghaving a plurality of circumferentially spaced dependent locking fingers111 which are releasably engageable in the locking recess 93 of theouter tubing string landing nipple 92. The fitting 110 has a pair oflateral ports 112 to admit control fluid to the safety valve from anannulus 113 defined between inner and outer tuhling strings andcommunicating at the surface with the control fluid line 44. The safetyvalve 103 includes circumferentially spaced radially movable lockingdogs 114 engageable in an internal locking recess 115 of the innertubing landing nipple section 105. A central body section of the safetyvalve holds the inner tubing string locking collets 111 against inwardmovement, thereby locking the inner tubing string within the outertubing string landing nipple 92 when the safety valve is locked inposition within the innertubing string so that a pressure differentialacross the safety valve, when closed, will not lift the safety valve andthe inner tubing string relative to the outer tubing string. The safetyvalve has upper and lower external seal assemblies 121 and 122,respectively, sealing around the valve with the bore walls of the innertubing string so that control fluid communicated through the annulus 113and the side ports 112 is directed to a side port 123 in the safetyvalve for controlling the opening and closing of the valve from thesurface.

A well system, as represented by FIGS. 4-A and 4-B, may originallyinclude only the outer tubing string which, when desired, is fitted witha well safety valve system embodying the invention. A suitable standardplug, not shown, is run by wireline into the outer tubing string andlocked at the recesses 95'for shutting in the well above the plug, Thewell is then opened at the well head and the inner tubing string is runinto the well until the collet fingers 1 1 1 expand into the outertubing string landing nipple locking recess 93. The well pressure isthen equalized across the plug, and the'plug is removed by wirelinetechniques. The safety valve 103 is then run by wireline into the innertubing string and locked at the lower end of the string by expanding thekeys 114 into the locking recesses 115. The central body portion 120 ofthe safety valve 103 holds the outer tubing string locking collets 111expanded in the recess 93. The seals 121 and 122 seal above the sideports 112 so that control fluid pressure is communicated from thesurface through the annulus 113 to the safety valve holding the valve atan open position.

When removal of the safety valve systemin FIGS. 4-A and 4-B is desired,the valve 113 is first removed by wireline and a standard well plug, notshown, is run through the inner tubing string into the landing nipple 94of the outer tubing string. With the well thus shut in, the well head isopened and the inner tubing string is lifted disengaging the lockingfingers 111 from the locking recess 93 o the landing nipple 92 of theouter tubing string. With the collet fingers disengaged, the innertubing string is removed from the outer tubing string through the wellhead. Thus, the well system shown in FIGS. 4-A and 4-B permits the outertubing string to be fitted with a removable inner tubing string which isheld in place by a safety valve releasably locked within the lower endof the inner tubing string so-that an existing well having a tubingstring with a landing nipple is readily converted to a safety valvesystem.

A still further form of well safety valve system embodying the inventionis illustrated in. FIGS. -A through 8-C wherein an outer tubing string130 having a smooth wall bore 131 is converted to a safety valve systemby the installationof an inner tubing string 132 and a safety valve 133.A well plug 134 is used in carrying out the precedure of installing thisparticular safety valve system in a well. Referring particularly toFIGS. 5-A, 5-H, and S-C, the well as initially equpped and produced hasthe outer tubing string 130 supported from the well head hanger 24 as inFIG. 1. A suitable standard Otis Type G Stop or Pack-off Anchor Stop 135is run with wireline equipment and techniques to a desired depth atwhich it is locked withthe wall of the bore of the outer tubing string.The stop 135 includes an inner locking member 140 and an outer lockingcollet 141 having a plurality of circumferentially spaced collet fingers142 which are shown expanded along the expander surface 143 of the innermember for locking the stop with the tubing wall. A locking wire 144holds the inner and outer members together when withdrawing the stop, asdescribed hereinafter. The upper end edge 145 of the stop provides asupporting surface for the wireline installable and removable landingnipple 135. After setting the bottom stop, the removable landing nipple135 is installed by wireline and set on the stop 136.

The landing nipple 135 is shown in FIGS. 5-A, S-B, and S-C positioned onthe stop 136 but not locked with the tubing string wall. The landingnipple comprises a tubular body having an upper portion 150a and areduced lower portion 15% for supporting the locking and sealingassemblies of the landing nipple. An annular retainer 151 is threaded onthe lower end of the reduced portion l50b of the landing nipple body forholding an expandable seal 152. An internal O-ring 153 seals between thebody and the retainer. A seal expander sleeve 154 is slidably disposedon the body above the seal 152. An O-ring 155 is positioned within aninternal annular recess of the expander for sealing between the expanderand the body. An expander collet is interlocked with the seal expander154 and slidable along the body. A collet locking sleeve 161 having anupper external annular flange portion 162 is slidably disposed along thebody interconnected by a shear pin 163 with the expander 160. A lockingcollet 164 having locking collet finger heads 165 is slidable on thesleeve 161 and connected thereto by a shear pin 170. An elongatedexternal operator sleeve 171 is slidably disposed over the body 150 andlocked thereon by a shear pin 171a for expanding the seal 152 and thelocking collet finger heads 165. The sleeve 171 has an upper internalannular flange 172 and a lower internal annular'flange 173 whichoverlaps the collet expander sleeve flange 162 positioned between theflange 162 and the upper end of the locking collet 164.

The body 150 of the removable landing nipple 135 has an upper internalannular locking recess 174, an intermediate internal annular lockingrecess 175, and a lower internal annular locking recess 180. Therernovable landing nipple is installed in the outer tubing 130 on thestop 136 with standard wireline equipment. The landing nipple is runinto the tubing 130 with the seal 152 relaxed and contracted and thelocking collet fingers 165 at upper non-locking positions as shown inFIGS 5-A, 5-B, and 5-C. When the landing nipple comes to rest on theupper end 145 of the stop, the outer sleeve 171 is jarred downwardlyforcing the locking and seal expander assembly held together by theshear pins 163 and comprising the seal assembly expander 154, the colletfinger expander 160, the collet assembly 164, and the sleeve colletexpander 161 downwardly against the seal 152 expanding the seal untilthe resistance against further expansion effects the shearing of the pin170. Initially, in order to release and jar the sleeve 171 downwardly,the pin 171a is sheared releasing the outer sleeve 171 on the body 150for downward movement. When the pin 170 is sheared, the flange 173 ofthe outer sleeve 171 forces the collet 164 downwardly against theexpander 160 which is held by the previously expanded seal assembly 152so that the collet fingers 165 are wedged along the expander 160 againstthe wall bore of the outer tubing locking the landing nipple againstupward movement in the outer tubing string.

After the wireline installation of the removable landing nipple 135 onthe stop 136, the well is shut in by the wireline installation of theplug 134. The plug is a suitable standard well tubing plug assemblyhaving a central mandrel 190 disposed within a tubular body comprisingan upper member 191, central members 192, 193, and 194, and a lowerouter member 195. plurality of locking dogs 200 are supported on thebody operated by a sleeve 201. A seal assembly 202 is supported on thebody between the members 192 and 193 for sealing around the plug withinthe landing nipple 135. An annular closure member 203 is secured by ashear pin 204 within the bore 205 of the lower body member 195.

The plug 134 is designed to seal against a pressure differential ineither an upwardly or a downwardly direction. After the plug 134 islowered into the landing nipple, the plug locking dogs 200 are expandedinto the landing nipple locking recess 175 locking the plug in placewithin the landing nipple. The pressure is then bled off the well byrelieving the pressure at the well head in the outer tubing string sothat the well may be opened with the pressure differential beingsustained by the plug 134. The locking collets 165 on the landing nippleprevent upward movement of the landing nipple while the seal 202 aroundthe plug and the seal 203 within the plug prevent well flow upwardlypast the plug.

The inner tubing string 132 is then run into the well. The inner tubingstring has a collet assembly along the lower end section of the stringcomprising a plurality of circumferentially spaced collet fingers210below a side 1 port 211 in thetubing stringnThe. string is provided withlocking recesses 212 for locking the well safety valve 133 in placewithin the innertubingstring. The inner tubing string is lowered in theouter string until the collet fingers 210 move into the upper end of thelanding nipple body 150 and expand into the annular locking recess 174ofthe body. The inner tubing string is spaced concentrically within theouter tubing string defining a control fluid annular passage 213 from tesurface into the landing nipple 135. The use of the plug 134 within theremovable landing nipple perm-its the tubing string, which may be ofsubstantial length such as 1,000 feet or more, to be inserted into theouter tubing string without the useofa stuffing box, which is notparticularly satisfactory for the insertion of such a long string oftubing.

After the inner tubing string 132 is installed in the outer tubingstring, wireline tools are run through the inner tubing string to theplug 134 which is jarred upwardly shearing the pin 204 withdrawing thecentral rod 190 permitting pressure equalization across the plug so thatwell pressure is again communicated through the tubing strings to thesurface. The plug is then removed by standard wireline procedures whcheffect the disengagement of the locking dogs 200 from the recess 175 ofthe landing nipple followed by removal of the complete plug from thetubing strings through the well head. The safety valve 133 is then runwith wireline tools through the inner tubing string 132 into the landingnipple 135 and locked at the recess 212 in the lower end of the innertubing string. The valve 133 is a standard valve assembly adapted to beset and retrieved by wireline methods. The valve includes lockingjdogs214 which are expandable into the inner tubing string locking recesses212 for locking the safety valve within the lower end portion of theinner tubing string 132. The valve body has upper and lower sealassemblies 215 and 220, respectively, for sealing with the 10 lower endof the bore of the inner tubing string and the bore of the landingnipple above and below a valve side port 221 leading to the fluidcontrol mechanism of the safety valve. The safety valve has an annularpiston 222 which is forced downwardly against aspring 223 by controlfluid pressure communicated through the port 221 to hold the ballelement 224 of the valve in an open position. Release of the fluidpressure against the piston 222 allows the spring to lift the valvecontrol mechanism upwardly closing the ball .224 to prevent flow throughthe bore of the safety valve. The body of the safety valve along acentral portion 225 is aligned within the inner tubing string colletfingers 210 holding the collet fingers in locked relationship with thelocking recess 174. Thus, the safety valve is locked within the lowerend portion of the inner tubing string and holds the tubing stringlocked with the landing nipple 135, which, in turn, is locked with thesmooth wall bore of the outer tubing string 130. Control fluid iscommunicated from the surface to the safety valve through the annularspace 213 between the inner and outer tubing strings.

When removal of the well saftty valve system, as

shown in tts complete form in FIGS. 8-A through 8-C,

is desired, the safety valve 133 is first removed by release of thelocking dogs 214 to permit the valve to be pulled through the innertubing string to the surface. The well plug 134 is then reinstalled inthe well through the inner tubing string and locked within the landingnipple 135 by expansion of the dogs 200 into the locking recess 175. Thepressure is then bled from the well at the surface and the inner tubingstring is withdrawn. Since the plug 134 has no structure aligned withand against the collet fingers 210 on the lower end of the inner tubingstring, the collet fingers are cammed inwardly out of the locking recess174 responsive to a lifting force on the tubing string from the surface.When the collet fingers release from the landing nipple, the innertubing string is lifted from the well through the well head. Afterremoval of the inner tubing string, the

central member 190 of the plug 134 is removed equalizing the pressureacross the bottom plug and the remainder of the plug is removed bywireline. The landing nipple is secured by a pulling tool at the upperend thereof lifting the outer sleeve 171 until the flange 173 engagesthe slip expander flange 162. The sleeve is jarred upwardly severing thepin 163 so that the slip expander sleeve 161 is pulled upwardly allowingthe slip expander to contract. When the sleeve 161 is lifted asufficient distance, the flange 161a engages the internal flange 164awithin the slip assembly head withdrawing the slips 165 from the slipexpander, thereby releasing the landing nipple 135 which is thenwithdrawn from the outer tubing string. The stop 163 then may besimilarly released and retrieved. The inner expander member 142 islifted from within the outer member 141 so that the slips 143 movedownwardly on the expander surface of the member 140, releasing theslips from the outer tubing string wall. When the slips are released andthe stop is further lifted, the retainer wire 144 engages the shoulder140a on the inner member so that the slip assembly is lifted with theinner member and the complete stop is removed by wireline from the outertubing string. 7

Thus, an outer tubing string provided with'a smooth inner wall, and thusno pro-installed landing nipple, is readily fitted with a well safetyvalve system embodying the invention. it will be recognized that thisparticular safety valve system includes a wireline operable landingnipple for locking the inner tubing string which then is held in placeby the safety valve which is locked within the lower end of the innertubing string.

A still further form of well safety valve system including a removablelanding nipple lockable at an outer tube landing string nipple includedin the original well installation is shown in FIGS. 9-A through 12 ofthe drawings. In this particular form of the invention, the well inwhich the safety valve system is installed is one in which an outertubing string 250 was initially run and set in the well. The tubingstring 250 includes an Otis Type S landing nipple 251 connected in theouter string by pipe couplings 252 and 253. The inclusion of such alanding nipple in a tubing string at selected depths at which well toolsmay in the future be installed in the well is often standard practice.The landing nipple ineludes an upper internal recess 254 and lowerlocking recesses 255. The safety valve system includes a removablelanding nipple 260, a well plug 261, an inner tubing string 262, and asafety valve 263.

Starting with the well equipped with only the outer tubing string 250and the landing nipple 251 empty, the first step in the procedure is thewireline installation of the removable landing nipple 260. The landingnipple 260 has a tubular body mandrel 270 provided near the upper endthereof with an internal annular locking recess 271 for the releasablelocking of the inner tubing string with the landing nipple. The nipple260 has an intermediate locking recess 272 for the locking of the plug261 within the landing nipple. A plurality of O- ring seals 273 aredisposed within external annular recesses along the central portion ofthe landing nipple body mandrel for sealing around the landing nipplewith the wall surface 274 defining the bore through the outer tubinglanding nipple 251. Below the O-ring seals 273 the body mandrel 270 isreduced in diameter at 275 and threaded externally along a lower endsection 280 for engagement of an annular retainer 281 which holds alocking collet 282 on the lower end portion of the body mandrel. Thelocking collet has a base annular ring portion 283 and a plurality ofcircumferentially spaced locking collet fingers 284 extending from thering upwardly along and around the body mandrel. The locking fingershave outer boss configurations adapted to fit the landing nipple lockingrecesses 255 of the outer tubing string landing nipple 251. The bodymandrel 270 has a plurality of circumferentially spaced longitudinalwindows 285 best illustrated in FIG. 12 which shows in explodedrelationship the lower end portion of the body mandrel 270 along withthe collet 282 and the retainer 281. The windows 285 extend from thelower end portion of the full diameter of the body mandrel 270 into thereduced diameter portion of the body mandrel and are spaced to receivethe locking collet fingers 284. When the locking collet 282 istelescopi- 1 cally disposed on the body mandrel held by the retainer-281, the collet fingers project radially partially inwardly into thewindows 285 and the bosses of the fingers project radially outwardlybeyond the full diameter of the body mandrel so that at the normalrelaxed positions of the collet fingers they are receivable in thelocking nipple recesses 255.

When the collet 282'is assembled on the body mandrel, the base ends ofthe collet fingers 284 are slightly within the lower ends 285a of thewindows 285 so that the collet fingers 284 may be compressed inwardlyinto the bore of the body mandrel 270 during insertion and withdrawal ofthe landing nipple 260 at the outer tubing string landing nipple 251. Aninternal supporting shoulder 290 is provided around the bore through thelanding nipple body mandrel 270 to limit the downward movement of theplug 261 in the landing nipple 270.

The landing nipple 270 is installed by standard wireline procedures by awireline running tool of suitable design engaged at the internal recess271 of the landing nipple body mandrel 270. The landing nipple islowered through the outer tubing string 250 to the landing nipple 251 inthe outer tubing string. During the downward travel of the landingnipple 260 the collet fingers 284 are held compressed inwardly into thebody mandrel windows 285 by the bore wall of the outer tubing string.The landing nipple 260 moves into the tubing string landing nipple 251until the collet fingers 284 are aligned with the locking recesses 255which permit the collet fingers to spring radially outwardly intolocking relationship in the recesses. The shoulders 284a on the colletfingers provide an abrupt stop means for the collet fingers and thus thelanding nipple 260. A further precaution against movement of the landingnipple 260 below the tubing string landing nipple 251 is provided by thelarger diameter portion 270a of the body mandrel 270 which terminates ata shoulder 2701) which is larger in diameter than the bore through thelanding nipple 251 so that a malfunction of the collet fingers 284 willnot result in the landing nipple 260 going below the tubing stringlanding nipple 251.

Following the setting of the removable landing nipple 260 within theouter tubing string 250, the wirelinetype plug 261 is run into the welland locked in the landing nipple 260 for shutting in the wellpreparatory to the running of the inner tubing string 262. The plug 261is of a suitable standard design including a tubular body assembly 300comprising central tubular members 301 and 302, a lower solid lockingrod member 303 and upper handling and locking structure including astandard Otis X-type locking mandrel 304 having locking dogs 305 and aninternal annular handling recess 310 for connecting the tool with awireline running tool. An external seal assembly 311 is supported on theplug body for sealing around the plug with the bore surface of theremovable landing nipple 260. An internal sleeve valve 312 is slidablydisposed within the bore of the body member 302 for movement between anupper closed position and a lower open position within the bore forcovering and uncovering a side port 313 in .the plug body member 302.The fit of the plug body within the removable landing nipple body 270below the seal assembly 311 on the plug body is sufficiently loose thatwell pressure is readily communicated within the removable landingnipple around the plug body to the side port 313. Thus, movement of thevalve 312 downwardly to a lower position at which the locking colletfingers 312a of the valve engage the internal shoulder 314 uncovers theside port 313 allowing equalization of well pressure across the plug andcommunicating into the bore 315 of the plug which opens upwardly intothe tubing string above the plug. The valve 312- is movable by suitablestandard wireline tools.

With the removable landing nipple 260 installed as previously described,the plug 261 is run in on a wireline into the landing nipple bodymandrel 270 against the stop shoulder 290. The locking dogs 305 of theplug expand into the locking recess 272 locking the plug within theremovable landing nipple. The solid rod portion 303 of the plug bodyprojects within the removable landing nipple collet fingers 284preventing inward movement of the collet fingers and thereby holdingthem at their normal locking relationship in the locking recesses 255 sothat as the pressure is bledfrom the well at the well head applyingupward well pressure to the plug, the rod 303 holds the removablelanding nipple locked within the outer tubing string landing nipple 251.The upward well pressure differential across the plug cannot force theplug and the removable landing nipple upwardly in the outer tubingstring. The O-ring seals 273 around the removable landing nipple preventflow around the body mandrel 270 while the seal assembly 311 on the plugprevents fluid flow within the body mandrel 270 around the plug.

With the plug 261 set in the landing nipple 260, the well is bled downand opened at the well head for insertion of the inner tubing string262. The lowerend portion of the inner tubing string has a set ofcircumferentially spaced locking collet fingers 320 whichfare receivablein the locking recess 271 of the removable landing nipple 260.Additionally, the inner tubing string has a side port 321 above thecollet fingers 320. Above the side port 321 the lower end portion of theinner tubing string is provided with locking recesses 322 for thereleasable locking of the safety valve 263 within the lower end of theinner tubing string. The

inner tubing string is run into the outer tubing string until the colletfingers 320 enter the upper end of the removable landing nipple bodymandrel 270 and spring outwardly into locking relationship with thelocking recess 271 of the landing nipple body. A wireline tool is thenrun into the inner tubing string through the string to the plug 261engaging the internal sleeve valve 312 which is forced downwardly untilthe collet fingers 312a engage the stop shoulder 314 uncovering the sideport 313 of the plug body. The pressure is equalized across the plugthrough the side port 313 to permit removal of the plug. The plug isthen retrieved by engagement of a suitable wireline pulling tool withthe handling recess 310 of the plug body releaslng the mandrel lockingdogs 305 and withdrawing the plug from the removable landing nipplebore.

The well safety valve 263 is then run with wireline equipment into theinner tubing string where it is releasably locked within the lower endof the tubing string and the removable landing nipple 260. The safetyvalve is of suitable standard design having a tubular body mandrel 330on which'is secured a locking mandrel 331 having a set of locking dogs332 provided with outer bosses which fit the inner tubing string lockingrecesses 322. The safety valve has an external seal assembly 333 forsealing around the safety valve with the bore wall of the inner tubingstring below the locking recesses 322. The safety valve body also has alower seal assembly 334 for sealing with the bore wall of the removablelanding nipple body mandrel 270. Between the upper and lower sealassemblies of the safety valve,

the body of the valve has a side port 335 leading to an annular pistonchamber 340 in which is disposed an annular valve operator 341 having anannular piston 342 movable responsible to control fluid pressurecommunicated'through the side port 335. The valve operator rotates aball valve 343 for closing and opening the bore through the safetyvalve. The valve operator is biased upwardly toward a valve-openposition by a spring 344. The lower end portion of the safety valve bodycomprises atubular locking member 345 which, when the valve is locked inplace in the removable landing nipple, extends in looking relationshipthrough the collet fingers 284 so that the landing nipple collet fingersare prevented from inward movement. Thus, thelower end portion of thesafety valve holds the removable landing nipple in lockedrelationshipinthe outer tubing string landing nipple 251 so long as'the safety valveis in place within the landing nipple. The body of the safety valvealong the upper central portion of the valve above the side port 335issized to fit within and along the inner tubing-string locking colletfingers 320 holding the fingers in locked relationship in the lockingrecess of the body mandrel 270 of the removable landing nipple 260 sothat so long as the safety valve isheld within the removable landingnipple in the position shown, the inner tubing string is maintainedlocked with the removable landing nipple. Thus, the lower end portion ofthe safety valve locks the removable landing nipple in the fixed landingnipple of the outer tubing string while the upper central portion of thesafety valve body locks the inner tubing string with theremovablelanding nipple and the safety valve is locked by the dogs 332 in therecesses 322 of theinner tubing-string.

The inner tubing string 262 is concentrically spaced within the outertubing string 250defi'ningan annular control fluid flow passage 350extending from the surface to the valve 263 for communicating controlfluid to the valve to hold the valve in an open position. The pressureis ommunicated along the annular flow passage to the tubing side port321 and also along the 06]- let fingers 320 to the side port 3350f thesafety valve between its upper and lower seal assemblies 333 and 334.The control fluid pressure is communicated through the side port intothe piston chamber 340 for holding the piston 342 downwardly at avalve-open position. So long as the well is produced, the-ball valve 343is held open by the control fluid communicated from .the surface. When apredetermined condition develops responsive to which the valve isarranged to close, the control fluid pressure is reduced permitting thespring 344 to lift the piston 342 rotating the valve 343 to a closedposition. The application of a pressure differential across the valvetends to lift the valve in the inner tubing string applying an upwardforce to the string through the locking dogs 332. This upward force iscommunicated through the inner tubing string locking fingers 320 to themandrel of the removable landing nipple 260.. The fingers 320 are heldlocked by the presence of the safety valve through the fingers in thebore of the removable landing nipple. Additionally, the upward forcecommunicated through the locking fingers 320 tends to lift the removablelanding nipple which also is held locked in place by the collet fingers284 which are prevented from inward movement by the tubular member 345of the safety valve extending cause no pressure differential now existsacross the removable landing nipple. The well plug 261 is again run inthe inner tubing string and locked within the removable landing nippleat the position shown in FIGS. 9-A, 9-B, and 9-C, and the well pressureis bled off at the well head so that the well head is opened forretrieval of the inner tubing string 262- With a pressure differentialagain across the removable landing nipple, the nipple is held in placeby the rod portion 303 of the plug. The inner tubing string is liftedcamming the collet fingers 320 inwardly from the locking recess 271releasing the inner tubing string from the landing nipple body 270.After the inner tubing string is fully withdrawn, the pressure isequalized across the end plug by "using wireline techniques to shift thesleeve valve 312 to the open position, subsequent to which the plug isretrieved from the well through the outer tubing string. The landingnipple 260 is then recovered by use of a wireline operated pulling'toolapplying an upward force to the upper end of the landing nipple at therecess 310. The upward force cams the locking collet fingers 284inwardly into the lateral windows 285 releasing the collet fingers fromthe recesses 255 permitting the landing npple to be withdrawn from theouter tubing string.

Thus, the -well safety valve system of FIGS. 9-A through 12 permits theconversion of an existing well having a tubing string provided with alanding nipple, such as the nipple 251, to a safety valve system. Thesystem includes a removable landing nipple lockable within the tubingstring landing nipple and a removable inner tubing string with both theremovable landing nipple and the inner tubing string being locked withinthe outer tubing string by the well safety valve. The removable landingnipple and the well safety valve and plug are all set and retrieved bywireline techniques.

It will be recognized that each of the illustrated and described formsof well safety valve systems includes mechanism for converting varioustypes of well systems to include a safety valve controllable from thesurface through an annular control fluid flow passage. In each form ofthe invention the annular flow passages are defined by concentricallydisposed inner and outer tubing strings; the inner tubing string isreleasably locked at a lower end thereof with structure secured to theouter tubing string at the safety valve depth; and the inner string isheld in such locked relationship by the presence of the well safetyvalve. The well safety valve is biased open by control fluid pressureand closes to shut off communication into the inner tubing stringresponsive to the occurrence of a predetermined condition. The controlfluid is communicated from the surface and responds to any one or moreof a number of desired opeating conditions. With the exception vof therunning of the inner tubing string, the other procedures carried out inthe well bore may be handled by wireline techniques. in one form of theinvention, an original well installation includes a landing nipple intowhich the inner tubing string is coupled and held by the safety valvewhich is releasably locked within the lower end of the inner tubingstring. In another form of the invention a removable landing nipple isreleasably locked at a landing nipple provided in the outer tubingstring with the inner tubing string then being coupled into theremovable landing nipple and held by a safety valve supported in thelower end of the inner tubing string. In a still further form of theinvention a removable landing nipple is supported and locked at adesired depth along a smooth wall bore of the outer tubing string withthe inner tubing string being coupled into the removable landing nippleand held by a safety valve supported at the lower end of the innertubing string. In a still further form of the invention a removablelanding nipple is releasably locked at an outer tubing string landingnipple and supported in locked relationship by the removable well plugand safety valve utilized. The plug is supported in the removablelanding nipple, and the safety valve, when in operation, is supported inthe lower end of the inner tubing string extending through the removablelanding nipple locking both the tubing string in the removable landingnipple and the removable landing nipple in the outer tubing stringlanding nipple.

What is claimed and desired to be secured by Letters Patent is:

1. A well safety valve system comprising: a first outer tubing stringsupported in a well; first locking means associated with said firsttubing string at a predetermined depth along said string; a second innertubing string supported in spaced concentric relationship within saidfirst tubing string defining an annular control fluid flow passagebetween said tubing strings from a surface end thereof along saidstrings; said second tubing string including second locking means forreleasably locking said string with said first locking mean, said secondlocking means being held in locked relationship with said first lockingmeans by a safety valve positioned within said tubing stringcommunicating with said annular flow passage between said strings, saidsafety valve being insertable and removable through said second tubingfrom the surface.

2. A well safety valve system in accordance with claim 1 wherein saidlocking means coupled with said first tubing includes an internalannular locking recess and said second-tubing string is provided withlocking collet fingers receivable in said locking recess of first tubingstring and held in said recess by said safety valve.

3. A well safety valve system in accordance with claim 2 including asafety valve releasably locked in said tubing strings holding said innertubing string in locked relationship with said outer tubing string.

4. A well safety valve system in accordance with claim 2 wherein saidlocking means coupled with said first tubing string comprises a conduitsection connected in said first tubing string and having an annularlocking recess therein for releasable connection of said second tubingstring with said first tubing string.

5. A well safety valve system in accordance with claim 4 including asafety valve releasably locked in said tubing strin holding said innertubing string locked with said outer tubing string.

6. A well safety valve system in accordance with claim 4 wherein saidsecond tubing string is provided with external seal means spaced fromsaid locking fingers and adapted to seal around said second tubingstring within said first tubing string on opposite sides of a side portin said first tubing string leading to a control fluid line connectedwith said first tubing string and communcating with said side port.

7. A well safety valve system in accordance with claim 2 wherein saidlocking means coupledwith said first tubing string comprises a bottomstop releasably locked along a smooth wall bore section of said firsttubing string and a landing nipple supported on said bottom stop andreleasably locked with said smooth wall bore section of said firsttubing string; and said internal locking recess for said locking fingersof said second tubing string is provided in said landing nipple forreleasably locking said second tubing string with said landing nipple;said safety valve being supportable at the lower end of said secondtubing string and aligned with said locking fingers for holding saidfingers in locked relationship with said landing nipple when said safetyvalve is locked with said second tubing string.

8. A well safety valve system in accordacne with claim 7 wherein saidremovable landing nipple is provided with expandable and contractiblelocking dogs and an external annular seal for sealing around said nipplewith the wall surface of the bore of said first tubing string.

9. A well safety valve system in accordance with claim 7 including aremovable well plug for closing a bore through said landing nipple whensaid second tubing string is being run in and retrieved from said firsttubing string and a well safety valve for support in said second tubingstring when said second tubing string is releasably locked with saidlanding nipple within said first tubing string.

10. A well safety valve system in accordance with claim 2 wherein saidlocking means coupled with said first tubing string includes a firstlanding nipple comprising a sectionyof said first tubing string and areleasably lockable second landing nipple having locking dogs forlocking said second landing nipple with said first landing nipple insaid first tubing string, said internal annular locking recess beingprovided in said second landing nipple forreleas ably locking, saidsecond tubing string withsaid second landing nipple, said locking dogsof said second landing nipple being held in locked relationship withsaid first landing nipple by a well plug when said well plug isreleasably locked in said second landing nipple and by a safety valvewhen said safety valve is releasably locked in said second landingnipple, said safety valve having a locking surface aligned with saidlocking fingers of said second tubing string for holding said tubingstring releasably locked with said second landing nipple when saidsafety valve is locked in place along said second tubing string and saidsecond landing nipple.

11. A well safety valve system in accordance with claim 10 including awell plug releasably lockable in said second landing nipple below saidlocking recess in said nipple and having a locking member disposed alongsaid locking dogs of said second landing nipple holding said dogs in.locked relationship in said locking recess in sadi first landing nippleand a well safety valve lockable in saidsecond tubing string and havinga locking surface alignable with said locking fingers of said secondtubing string for holding said fingers in locked relationship with saidlocking recess of said second landing nipple and having a locking memberdisposed through said locking dogs of said second landing nipple forholding said locking dogs in said locking recess of said first landingnipple when said safety valve is releasably locked along said firsttubing string, second tubing string, and said second landing nipple.

12. A method of fitting a well with a well safety valve controlled byfluid pressure communicated from a surface end of said well comprisingthe steps of: positioning a well plug in a first production tubingstring of said well substantially at a depth at whichsaid safety valveis to be set in said well; bleeding the pressure down in said firsttubing string above said well plug; inserting a second inner tubingstring in said first tubing string and running saidsecond tubing stringto safety valve depth in said first tubing string; releasably lockingsaid second tubing string with said first tubing string at said safetyvalve depth; increasing the pressure in said tubing strings above saidwell plug for equalizing the pressure across said well plug; removingsaid well plug from said tubing string through said second tubingstring; and installing a safety valve in said second tubing stringat apredetermined depth therein and aligned to releasably hold said secondtubing string in locked relationship with said first tubing string solong as said safety valve is locked in said tubing string.

13. A method in accordance with claim 12 wherein said inner tubingstringis releasably locked with a locking recess provided along said outerfirst tubing string;

14. A method of fitting a well in accordance with claim 12 wherein aremovable landing nipple is releasably locked in said first tubingstring and provided with a locking recess and said second tubing stringis releasably locked with said removable landing nipple in said firsttubing string.

15. A method of fitting and operating a well in accordance with claim 14wherein said removable landing nipple is supported on a bottom stopadapted to releasably lock with a smooth wall bore section of said firsttubing string.

16. A method of fitting and operating a well in accordance with claim 14wherein said first tubing string includes a landing nipple having alocking recess therein and said removable landing nipple is locked insaid first tubing string at said locking recess therein and held inlocking relationship with said first tubing stringby a member on a wellplug when supported in said removable landingnipple and a member on asafety valve when supported in said removable landing nipple and saidsafety valve additionally is aligned to lock said second tubing stringwith said removable landing nipple.

17. A well safety valve system comprising: a first tub ing stringsupported in a well bore, said first tubing string including a landingnipple forming a portion thereof at a depth in said well forinstallation of a safety valve, said landing nipple having a side portfor communication of 'control fluid pressure from a control line leadingto said landing nipple; saidl landing nipple having an internal annularlocking recess spaced from said side port for locking a well tool insaid landing nipple;

a second inner tubing string concentrically spaced within said firstouter tubing string defining an annular control fluid flow passage fromthe surface along said tubing strings to said landing nipple in saidfirst outer tubing string, said inner tubing string having lockingcollet fingers formed along said tubing string in the side wall thereoffor releasably locking said second inner tubing string with said lockingrecess at said landing nipple of said first outer tubing string; sealmeans disposed around said second inner tubing string for sealing aboveand below said side port in said landing nipple of I said first tubingstring whereby said side port is isolated from the bore of said firsttubing string when said second tubing string is disposed in and lockedwith said first tubing string; and said second tubing string havinginternal annular locking recess means spaced from said locking colletfingers for supporting a well safety valve in said second tubing stringalong said locking collet fingers holding said collet fingers in saidlocking recess

1. A well safety valve system comprising: a first outer tubing stringsupported in a well; first locking means associated with said firsttubing string at a predetermined depth along said string; a second innertubing string supported in spaced concentric relationship within saidfirst tubing string defining an annular control fluid flow passagebetween said tubing strings from a surface end thereof along saidstrings; said second tubing string including second locking means forreleasably locking said string with said first locking mean, said secondlocking means being held in locked relationship with said first lockingmeans by a safety valve positioned within said tubing stringcommunicating with said annular flow passage between said strings, saidsafety valve being insertable and removable through said second tubingfrom the surface.
 2. A well safety valve system in accordance with claim1 wherein said locking means coupled with said first tubing includes aninternal annular locking recess and said second tubing string isprovided with locking collet fingers receivable in said locking recessof first tubing string and held in said recess by said safety valve. 3.A well safety valve system in accordance with claim 2 including a safetyvalve releasably locked in said tubing strings holding said inner tubingstring in locked relationship with said outer tubing string.
 4. A wellsafety valve system in accordance with claim 2 wherein said lockingmeans coupled with said first tubing string comprises a conduit sectionconnected in said first tubing string and having an annular lockingrecess therein for releasable connection of said second tubing stringwith said first tubing string.
 5. A well safety valve system inaccordance with claim 4 including a safety valve releasably locked insaid tubing strin holding said inner tubing string locked with saidouter tubing string.
 6. A well safety valve system in accordance withclaim 4 wherein said second tubing string is provided with external sealmeans spaced from said locking fingers and adapted to seal around saidsecond tubing string within said first tubing string on opposite sidesof a side port in said first tubing string leading to a control fluidline connected with said first tubing string and communcating with saidside port.
 7. A well safety valve system in accordance with claim 2wherein said locking means coupled with said first tubing stringcomprises a bottom stop releasably locked along a smooth wall boresection of said first tubing string and a landing nipple supported onsaid bottom stop and releasably locked with said smooth wall boresection of said first tubing string; and said internal locking recessfor said locking fingers of said second tubing string is provided insaid landing nipple for releasably locking said second tubing stringwith said landing nipple; said safety valve being supportable at thelower end of said second tubing string and aligned with said lockingfingers for holding said fingers in locked relationship with saidlanding nipple when said safety valve is locked with said second tubingstring.
 8. A well safety valve system in accordacne with claim 7 whereinsaid removable landing nipple is provided with expandable andcontractible locking dogs and an external annular seal for sealingaround said nipple with the wall surface of the bore of said firsttubing string.
 9. A well safety valve system in accordance with claim 7including a removable well plug for closing a bore through said landingnipple when said second tubing string is being run in and retrieved fromsaid first tubing string and a well safety valve for support in saidsecond tubing string when said second tubing string is releasably lockedwith said landing nipple within said first tubing string.
 10. A wellsafety valve system in accordance with claim 2 wherein said lockingmeans coupled with said first tubing string includes a first landingnipple comprising a section of said first tubing string and a releasablylockable second landing nipple having locking dogs for locking saidsecond landing nipple with said first landing nipple in said firsttubing string, said internal annular locking recess being provided insaid second landing nipple for releasably locking said second tubingstring with said second landing nipple, said locking dogs of said secondlanding nipple being held in locked relationship with said first landingnipple by a well plug when said well plug is releasably locked in saidsecond landing nipple and by a safety valve when said safety valve isreleasably locked in said second landing nipple, said safety valvehaving a locking surface aligned with said locking fingers of saidsecond tubing string for holding said tubing string releasably lockedwith said second landing nipple when said safety valve is locked inplace along said second tubing string and said second landing nipple.11. A well safety valve system in accordance with claim 10 including awell plug releasably lockable in said second landing nipple below saidlocking recess in said nipple and having a locking member disposed alongsaid locking dogs of said second landing nipple holding said dogs inlocked relationship in said locking recess in sadi first landing nippleand a well safety valve lockable in said second tubing string and havinga locking surface alignable with said locking fingers of said secondtubing string for holding said fingers in locked relationship with saidlocking recess of said second landing nipple and having a locking memberdisposed through said locking dogs of said second landing nipple forholding said locking dogs in said locking recess of said first landingnipple when said safety valve is releasably locked along said firsttubing string, second tubing string, and said second landing nipple. 12.A method of fitting a well with a well safety valve controlled by fluidpressure communicated from a surface end of said well comprising thesteps of: positioning a well plug in a first production tubing string ofsaid well substantially at a depth at which said safety valve is to beset in said well; bleeding the pressure down in said first tubing stringabove said well plug; inserting a second inner tubing string in saidfirst tubing string and running said second tubing string to safetyvalve depth in said first tubing string; releasably locking said secondtubing string with said first tubing string at said safety valve depth;increasing the pressure in said tubing strings above said well plug forequalizing the pressure across said well plug; removing said well plugfrom said tubing string through saId second tubing string; andinstalling a safety valve in said second tubing string at apredetermined depth therein and aligned to releasably hold said secondtubing string in locked relationship with said first tubing string solong as said safety valve is locked in said tubing string.
 13. A methodin accordance with claim 12 wherein said inner tubing string isreleasably locked with a locking recess provided along said outer firsttubing string.
 14. A method of fitting a well in accordance with claim12 wherein a removable landing nipple is releasably locked in said firsttubing string and provided with a locking recess and said second tubingstring is releasably locked with said removable landing nipple in saidfirst tubing string.
 15. A method of fitting and operating a well inaccordance with claim 14 wherein said removable landing nipple issupported on a bottom stop adapted to releasably lock with a smooth wallbore section of said first tubing string.
 16. A method of fitting andoperating a well in accordance with claim 14 wherein said first tubingstring includes a landing nipple having a locking recess therein andsaid removable landing nipple is locked in said first tubing string atsaid locking recess therein and held in locking relationship with saidfirst tubing string by a member on a well plug when supported in saidremovable landing nipple and a member on a safety valve when supportedin said removable landing nipple and said safety valve additionally isaligned to lock said second tubing string with said removable landingnipple.
 17. A well safety valve system comprising: a first tubing stringsupported in a well bore, said first tubing string including a landingnipple forming a portion thereof at a depth in said well forinstallation of a safety valve, said landing nipple having a side portfor communication of control fluid pressure from a control line leadingto said landing nipple; said landing nipple having an internal annularlocking recess spaced from said side port for locking a well tool insaid landing nipple; a second inner tubing string concentrically spacedwithin said first outer tubing string defining an annular control fluidflow passage from the surface along said tubing strings to said landingnipple in said first outer tubing string, said inner tubing stringhaving locking collet fingers formed along said tubing string in theside wall thereof for releasably locking said second inner tubing stringwith said locking recess at said landing nipple of said first outertubing string; seal means disposed around said second inner tubingstring for sealing above and below said side port in said landing nippleof said first tubing string whereby said side port is isolated from thebore of said first tubing string when said second tubing string isdisposed in and locked with said first tubing string; and said secondtubing string having internal annular locking recess means spaced fromsaid locking collet fingers for supporting a well safety valve in saidsecond tubing string along said locking collet fingers holding saidcollet fingers in said locking recess of said landing nipple of saidfirst tubing string when said safety valve is locked in said secondtubing string whereby said safety valve communicates with said annularflow passage between said tubing strings for controlling fluid flow intosaid second tubing string and holding said second tubing string inlocked relationship with said first tubing string.
 18. A well safetyvalve system in accordance with claim 17 including a safety valvereleasably locked i1 said second tubing string at said locking recesstherein, said safety valve 0aving spaced seal means for sealing aroundsaid valve with the inner wall defining the bore of said second tubingstring above and below said collet fingers in said second tubing string.19. A well safety valve system for controlling flow in a well through asafety valve communicating with the surface end of said well through aconcentric control fluid flow passage comprising: a first outer tubingstring supported in said well for producing well fluids therefrom, saidfirst tubing string including a landing nipple having an internalannular locking recess therein for releasably locking well tools in saidfirst tubing string at a depth adapted for use of a well safety valve insaid tubing string; a second tubing string concentrically spaced withinsaid first tubing string and extending to said landing nipple in saidfirst tubing string, said second tubing string having a plurality ofcircumferentially spaced locking collet fingers receivable in saidlocking recess of said landing nipple of said first tubing string forreleasably locking said second tubing string with said landing nipple ofsaid first tubing string; and said second tubing string having internallocking recess means spaced from said locking collet fingers forsupporting a safety valve in said second tubing string, said safetyvalve having a body surface portion aligned with said locking colletfingers of said second tubing string for holding said second tubingstring in locked relationship with said first tubing string when saidsafety valve is releasably locked in said second tubing string.
 20. Awell safety valve system in accordance with claim 19 including a wellsafety valve releasably locked in said second tubing string at saidlocknng recess thereof, said safety valve having external seal means forsealing around said valve within said second tubing string above saidlocking collet fingers thereon and for sealing within said landingnipple of said first tubing string below said collet fingers on saidsecond tubing string whereby control fluid pressure is directed from anannular space around said second tubing string within said first tubingstring to fluid pressure responsive means within said safety valve forcontrolling said safety valve by control fluid pressure communicated tosaid valve from the surface.
 21. A well safety valve system forcontrolling a safety valve by control fluid pressure communicated tosaid valve through an annular fluid flow passage extending from asurface end of a well comprising: a first outer tubing string disposedin said well extending to a production depth therein; a bottom stopreleasably locked with a smooth wall bore section of said first tubingstring; a releasably locked landing nipple supported on said bottom stopin said first tubing string, said landing nipple having first and secondspaced internal locking recesses therein for releasably locking a wellplug in said landing nipple and releasably locking a second inner tubingstring with said landing nipple, said landing nipple having lockingmeans thereon for locking said landing nipple with said smooth wall boresection of said first tubing string against said bottom stop; a secondinner tubing string supported in concentric spaced relationship withinsaid first tubing string, said second tubing string having a pluralityof spaced longitudinal locking collet fingers at the lower end thereoffor releasably locking said tubing string with said second of saidlocking recesses in said removable landing nipple; and said secondtubing string having locking recesses therein spaced from said lockingcollet fingers for releasably supporting a well safety valve at thelower end of said second tubing string at a position at which saidsafety valve is aligned within said locking collet fingers on saidsecond tubing string holding said collet fingers in locked relationshipwith said second locking recess of said landing nipple when said safetyvalve is locked in said second tubing string and said second tubingstring is interlocked with said landing nipple.
 22. A well safety valvesystem in accordance with claim 21 including a well safety valvereleasably locked at said locking recess in said second tubing stringand having an external wall portion of said valve extending along saidlocking collet fingers holding said collet fingers of said second tUbingstring locked with said removable landing nipple, said safety valvehaving external seal means spaced along a body portion thereof sealingwith said second tubing string above said locking collet fingers andwith said landing npple below said collet fingers for directing controlfluid pressure from said annular control fluid flow passage between saidtubing strings into a side port in said safety valve for controllingsaid safety valve responsive to fluid pressure from the surface end ofsaid well.
 23. A well safety valve system in accordance with claim 21wherein said removable landing nipple is provided with expandable andcontractible locking fingers for locking said landing nipple with saidsmooth wall bore section of said first tubing string and said landingnipple is provided with an external annular seal for sealing around saidnipple with said bore wall of said first tubing string.
 24. A wellsafety valve system for controlling a well safety valve by control fluidpressure communicated to said valve through an annular control fluidflow passage extending from the surface end of a well to said valve,comprising: a first outer tubing string supported in said well, saidtubing string including a landing nipple disposed at safety valve depthin said well along said first tubing string, said first landing nipplehaving an internal locking recess therein; a removable second landingnipple having locking dogs engageable in said locking recess of saidfirst landing nipple of said first tubing string, said second landingnipple having a first locking recess therein for releasably locking asecond inner tubing string therewith and a second locking recess forreleasably locking a well plug in said landing nipple, said locking dogson said second landing nipple being lockable with said locking recess ofsaid first landing nipple in said first tubing string by means on a wellplug supported in said removable landing nipple when said well plug isin operating position in said landing nipple and by means on a wellsafety valve when said safety valve is supported in operating positionthrough said second landing nipple; and a second inner tubing stringsupported concentrically spaced within said first tubing string defininga fluid flow passage between said first and second tubing strings to thelower end of said second tubing string, said second tubing string havinglocking collet fingers extending from the lower end thereofcircumferentially spaced around said second tubing string and receivablein said first locking recess of said removable landing nipple, and saidsecond tubing string having locking recess means therein near the lowerend thereof spaced from said locking collet fingers for supporting awell safety valve within said second tubing string at a position atwhich a body portion of said safety valve extends through said lockingcollet fingers of said second tubing string holding said collet fingersin locked relationship with said removable landing nipple.
 25. A wellsafety valve system in accordance with claim 24 including a well plugreleasably lockable with said second locking recess of said secondlanding nipple and having a locking rod thereon for holding said lockingdogs of said removable landing nipple in locked relationship in saidlocking recess of said first landing nipple of said outer first tubingstring when said plug is releasably locked in said removable landingnipple and a safety valve releasably lockable with said locking recessmeans of said second tubing string, said safety valve being alignedalong a body portion thereof within said locking collet fingers on saidsecond tubing string for holding said fingers in locked relationshipwith said second landing nipple and said safety valve having a lockingmember along a lower end thereof disposed within said locking dogs ofsaid second landing nipple for holding said dogs in locked relationshipwith said locking recess of said first landing nipple of said firsttubing string when said sAfety valve is locked in position in saidsecond tubing string, and said safety valve having spaced seals thereonfor sealing with said second tubing string above said locking colletfingers thereon and with said second landing nipple below said lockingcollet fingers for directing control fluid from said annular flowpassage between said tubing strings to a side port in said safety valvefor controlling said safety valve responsive to said control fluid.